In the field of automotive industry, a lot of resources are and have been allocated towards developing systems for reducing the emissions of motive, or propulsion, systems by e.g. reducing the overall fuel consumption of internal combustion engines and propulsion systems comprising internal combustion engines, introducing systems and components such as exhaust gas catalyzers, etc.
Reduced fuel consumption has e.g. been achieved by providing supercharging systems, wherein a compressor is used for forced induction of an internal combustion engine. In more detail, intake manifold pressure is increased in order to decrease internal pumping and throttling losses which, in turn, allows for decreased fuel consumption. Such a system further enables downsizing of a vehicle engine without substantially interfering with the vehicle, and vehicle engine performance requirements.
In an internal combustion engine of piston type, gas exchange takes place via the normal flow of a homogeneous mixture of pure air mixed with fuel and outflow of the burnt mixture/exhaust through the intake and exhaust valves. After combustion and the working cycle's expansion in the cylinder the gas evacuates from the cylinder through the open exhaust valves.
In the case when an internal combustion engine is equipped with a turbocharger the turbine size, the turbine housing swallowing capacity and the turbine operating point affects the possible outflow. A restrictive state renders a higher pressure in the exhaust manifold than the less restrictive for example.
The exhaust gas pressure in the manifold in turn affects the volume and mass of burnt gases remaining in the cylinder when the exhaust valves are closed. The residual exhaust gases are very hot and remain in the cylinder when the intake process starts with the opening of the intake valve.
Exhaust gas catalyzers commonly comprise part of the exhaust system from the internal combustion engine, often having a honeycomb shaped ceramic material coated with a catalyst that reacts with the exhaust gases to convert the more harmful emissions into less harmful emissions. In order for the catalyst to work a number of conditions have to be fulfilled. Among these conditions the catalyst has a working temperature range outside of which the conversion rate is suboptimal to non-existing. Furthermore there are a number of other conditions that affect the performance of the exhaust gas catalyzer, such as air/fuel mixture and presence of other contaminants in the exhaust gases. Exhaust gas catalyzers are common components in modern vehicles and will therefore not be further described herein.
There are methods to bring and keep the exhaust gas catalyzer to its operating range that commonly comprise increasing the fuel ratio in the air/fuel mixture which as such may be counterproductive in terms of emissions. There is hence a need to provide a supercharging system that reduces emissions.